1. Technical Field
The present invention relates an electromagnetic flow meter having a converter and a flowtube, and more particularly, to a technology of detecting a miswiring between the converter and the flow/tube.
2. Related Art
Since an electromagnetic flow meter configured to measure a flow rate of conductive fluid by using electromagnetic induction is robust and has high precision, it is widely used for an industrial use. The electromagnetic flow meter is configured to enable conductive fluid to be measured to flow into a measurement tube, to which a magnetic field is applied in an orthogonal direction, and to measure a generated electromotive force. Since the electromotive force is proportional to a flow rate of the fluid to be measured, it is possible to obtain a volumetric flow rate of the fluid to be measured on the basis of the measured electromotive force.
FIG. 15 is a block diagram showing a configuration of an electromagnetic flow meter of the related art. As shown in FIG. 15, the electromagnetic flow meter 50 has a converter 500 and a flowtube 530.
The converter 500 has an excitation unit 501 configured to generate and output an excitation signal, a flow rate signal receiving unit 502 configured receive a flow rate signal, a flow rate calculation unit 503 configured to calculate a flow rate on the basis of the flow rate signal and an output unit 504 configured to display a measurement result and the like and to transmit the same to another apparatus.
The flowtube 530 has a core 531 around which a coil 532 is wound, a pair of detection electrodes 533 mounted to a piping 300 and an earth electrode 534.
The excitation signal output from the excitation unit 501 is input to the coil 532 through an excitation cable 541, and the flow rate signals from the detection electrodes 533 and earth electrode 534 are input to the flow rate signal receiving unit 502 through a signal cable 542.
For example, when newly mounting the electromagnetic flow meter 50 to the piping 300 or re-mounting the electromagnetic flow meter 50 demounted for maintenance and the like, a corresponding operation is generally performed in accordance with a sequence shown in FIG. 16. That is, the flowtube 530 is mounted to the piping 300 and the converter 500 is mounted at a predetermined mounting place (S11). Then, the excitation cable 541 and signal cable 542 configured to connect the flowtube 530 and the converter 500 each other are wired (S12).
A zero adjustment is performed before actually starting an operation. The zero adjustment is performed at a state where the piping 300 is filled with water (S13) and there is no flow (S14). When the zero adjustment is finished, the fluid to be measured in the piping 300 is enabled to flow at a normal state and the operation actually starts (S15).
[Patent Document 1] Japanese Patent Application Publication No. 2013-257276A
It is not necessarily required that the mounting place of the flowtube 530 and the mounting place of the converter 500 should be close to each other. Also, a plurality of electromagnetic flow meters is mounted in the neighborhood in many cases. For this reason, as shown in FIG. 17, originally, a converter A 500a and a flowtube A 530a should be connected to each other by an excitation cable and a signal cable and a converter B 500b and a flowtube B 530b should be connected to each other by an excitation cable and a signal cable. At this time, a miswiring may occur.
As aspects of the miswiring, for example, as shown in FIG. 18A, the signal cable of the converter A 500a may be connected to the flowtube B 530b. At this time, as shown in FIG. 18B, when the flowtube B 530b is connected to the converter B 500b by the excitation cable, the flow rate signal detected by the flowtube B 530b may be input to the converter A 500a. 
Also, as shown in FIG. 19A, the excitation cable of the converter A 500a may be connected to the flowtube B 530b. At this time, as shown in FIG. 19B, when the excitation cable from the converter B 500 is connected to the flowtube A 530a, the flow rate signal detected on the basis of the excitation signal from the converter B 500b may be input to the converter A 500a. 
Further, as shown in FIG. 20, the converter A 500a and the flowtube B 530b are connected to each other by the excitation cable and the signal cable and the converter B 500b and the flowtube A 530a are connected to each other by the excitation cable and the signal cable, so that the flowtubes 530a, 530b to be connected to the converter A 500a and the converter B 500b are mixed up each other.
When the miswiring occurs, it may be found in many cases because an assumed flow rate and a display value are not matched after the operation actually starts (FIG. 16: S15). In this case, the operation should be actually stopped and returned to the wiring process (S12) and the zero adjustment (S14) should be re-executed. Therefore, the time is wasted and the number of processes increases, which in turn increases the cost.